From what I understand, RF- and microwave-circuits needs separate ground planes to avoid coupling between signal and DC/digital currents. I'm currently involved in an RF-project where we're going to use a SPDT-switch to control the path of the signal. The switch is Mini-Circuits SWMA-2-50DR+.
What confuses me is the suggested PCB layout, which includes signal-ground and TTL-ground terminals on a shared plane that's grounded through a lot of vias. I can't see how the currents can be uncoupled with this geometry, and where the vias are supposed to go if I have two ground planes. I know that separate ground planes need interconnection to tame unwanted modes, but I find it strange that it happens on the signal/component-layer.
I'm sure the layout is sensible, but I just don't have the experience to understand it yet. Enlightenment would be very much appreciated.
Best regards -paw